Engineering topics

Xu, D.

Publications and source records attributed to Xu, D..

7 records

DOE OSTI2024

Advancements in Accelerator Physics and System Developments for the EIC

The development and enhancement of the Electron-Ion Collider (EIC) are founded on extensive research and development efforts aimed at achieving rigorous performance goals. This document outlines the crucial research and development (R&D) efforts that underpin the various systems and components of the EIC, including the polarized electron source and linear accelerator (linac) systems. Achieving the collider’s operational benchmarks relies on meticulously enhancing these components to optimize performance.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Beam Dynamics of the Strong Hadron Cooler ERL at the Electron-Ion Collider

The Strong Hadron Cooler Energy Recovery Linac (SHC-ERL) for the Electron-Ion Collider (EIC) is required to produce an electron beam with a bunch charge of 1 nC, an average current of 100 mA, and a beam energy of both 150 and 55 MeV, with strict requirements for the transverse emittance, slice energy spread, and longitudinal distribution. This paper covers the design in detail, including preliminary considerations of higher order effects and diagnostics.

Deitrick, K.↗

DOE OSTI2024

Design Overview of the Strong Hadron Cooler ERL at the Electron-Ion Collider

The Electron-Ion Collider (EIC) is currently under development to be built at Brookhaven National Lab and requires cooling during collisions in order to preserve the quality of the hadron beam despite degradation due to intra-beam scattering and beam-beam effect. An Energy Recovery Linac (ERL) is being designed to deliver the necessary electron beam for Coherent electron Cooling (CeC) of the hadron beam, with an electron bunch charge of 1 nC and an average current of 100 mA; two modes of operation are being developed for 150 and 55 MeV electrons, corresponding to 275 and 100 GeV protons. The injector of this Strong Hadron Cooler ERL (SHC-ERL) is shared with the Injection Cooler ERL, which cools lower energy proton beams via bunched beam cooling, as used in the Low Energy RHIC electron Cooling (LEReC). This talk introduces the layout and presents a high-level overview of the design.

Deitrick, K.↗

NASA NTRS2014

A Multi-Wavelength Investigation of the Radio-Loud Supernova PTF11qcj and its Circumstellar Environment

We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L (sub 5 gigahertz) approximates 10 (sup 29) ergs per second per hertz). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of approximately 10 (sup -4) the mass of the sun per year times (v (sub omega) divided by 1000 kilometers per second), and a velocity of approximately 0.3-0.5 c (the speed of light in a vacuum) for the fastest moving ejecta (at around 10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude M (sub r) approximately equal to -13 mag may have occurred approximately 2.5 years prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

Radio↗

NASA NTRS2012

Identifying the Location in the Host Galaxy of Short GRB 1111l7A with the Chandra Sub- Arcsecond Position

We present our successful program using Chandra for identifying the X-ray afterglow with sub-arcsecond accuracy for the short GRB 111117A d iscovered by Swift and Fermi. Thanks to our rapid target of opportuni ty request, Chandra clearly detected the X-ray afterglow, whereas no optical afterglow was found in deep optical observations. Instead, we clearly detect the host galaxy in optica; and also in near-infrared b ands. We found that the best photometric redshift fitofthe host is z = 1.31:(+0.46/-0.23) (90% confidence), making it one of the highest redshift short GRBs. Furthermore, we see an offset of 1.0+/-O.2 arcseco nds, which corresponds to 8.4+/-1.7 kpc aSBuming z= 1.31, between the host and the afterglow position. We discuss the importance of using Chandra for obtaining sub-arcsecond localization of the afterglow in X -rays for short GRBs to study GRB environments in great detail.

Sakamoto, Takanori↗

NASA NTRS2007

Detection of GRB 060927 at zeta = 5.47: Implications for the Use of Gamma-Ray Bursts as Probes of the End of the Dark Ages

We report on follow-up observations of the gamma-ray burst GRB 060927 using the robotic ROTSE-IIIa telescope and a suite of larger aperture groundbased telescopes. An optical afterglow was detected 20 s after the burst, the earliest rest-frame detection of optical emission from any GRB. Spectroscopy performed with the VLT about 13 hours after the trigger shows a continuum break at lambda approx. equals 8070 A, produced by neutral hydrogen absorption at zeta = 5.6. We also detect an absorption line at 8158 A which we interpret as Si II lambda 1260 at zeta = 5.467. Hence, GRB 060927 is the second most distant GRB with a spectroscopically measured redshift. The shape of the red wing of the spectral break can be fitted by a damped Ly(alpha) profile with a column density with log(N(sub HI)/sq cm) = 22.50 +/- 0.15. We discuss the implications of this work for the use of GRBs as probes of the end of the dark ages and draw three main conclusions: i) GRB afterglows originating from zeta greater than or approx. equal to 6 should be relatively easy to detect from the ground, but rapid near-infrared monitoring is necessary to ensure that they are found; ii) The presence of large H I column densities in some GRBs host galaxies at zeta > 5 makes the use of GRBs to probe the reionization epoch via spectroscopy of the red damping wing challenging; iii) GRBs appear crucial to locate typical star-forming galaxies at zeta > 5 and therefore the type of galaxies responsible for the reionization of the universe.

Ruiz-Velasco, A. E.↗

NASA NTRS2003

Progress in GaAs Metamorphic HEMT Technology for Microwave Applications. High Efficiency Ka-Band MHEMT Power MMICs

This paper reviews recent progress in the development of GaAs metamorphic HEMT (MHEMT) technology for microwave applications. Commercialization has begun, while efforts to further improve performance, manufacturability and reliability continue. We also report the first multi-watt MHEMT MMIC power amplifiers, demonstrating up to 3.2W output power and record power-added efficiency (PAE) at Ka-band.

Smith, P. M.↗